1. Description of the Invention
This invention relates to valves, and more particularly, to a valve containing one or more flow lines with a power driven actuator arranged relative to the flow lines within the valve to determine the order, duration or magnitude of flow through each of the several lines.
2. Prior Art
The valve and associated hardware in an ink recirculating system for ink jet printing apparatus is very small. Therefore the operating capacity of the valve and the other associated hardware is limited. The pump used to control the flow around the whole circulating system operates at a pressure sufficient to force the ink through the head and onto the medium to be printed or to gutter without splatter and wetting of other parts in the ink jet printing apparatus. Typical valves for use with this pump in an ink recirculating system inherently have both the inlet valve and the vent valve opened simultaneously during minute periods of operation, even though there is an effort to minimize this. When both of the valves are opened simultaneously over a period of operating time, the pressure already built up in the system is gradually lost. This results in the pump having a tendency to over exceed its pumping capacity and the pressure becoming insufficient to force the ink stream to the gutter without contamination of other parts of the printing apparatus. This leads to a shutdown in the ink recirculating system and/or damage to the pump itself.
Another valve is known which purports to open one port simultaneously with the closing of another port. Although this substantially occurs, there is a small period of time when both are open. In this valve, the two ports are located directly opposite each other with a valve closing member located between the two ports. In normal operation, the valve closing member is located adjacent one of the two ports, such that when the valve closing member is actuated, it leaves the first port and moves very quickly to the other port and closes it. There is a small period of time when both ports are opened simultaneously, namely, when the valve closing member is traveling to the other port. This valve if used in a high pressure ink recirculating system would cause a gradual loss of pressure and the pump would start rattling and it would have a tendency to over exceed its pump rate.
Another problem with this particular valve when used in a high pressure system is that it can contaminate other associated hardware in the recirculating sytem due to the small period of time when both ports are opened simultaneously. If the opened port through which the fluid is entering the valve has to wait until the valve closing member translates the distance between the two ports to be closed, the flow of fluid through it will continue and this fluid can enter the other now opened port or continue through the flow lines to the outside where it can dribble onto other associated hardware.
Although I have described pressure loss and other problems that occur in high-pressure small volume systems and valves, it should be understood that these same problems can occur in high-pressure large volume systems and valves. The elimination of these problems would be a desirable effect in both systems.